The present invention relates to a dual band polarization filter which includes a hollow waveguide with waveguide couplings for four signals, means being provided to effect frequency and polarization separation of the four signals. Each of the four signals has a frequency in one of two different frequency bands and is polarized in one of two orthogonal directions.
Such a dual band polarization filter is disclosed in U.S. Pat. No. 3,978,434. This filter is equipped with relatively complicated means for separating the frequency bands and polarizations to meet particularly high demands, imposed in particular with connection with satellite radio communications, with respect to high polarization decoupling, low losses, and high decoupling between the signal paths of different frequency bands.
The extremely high demands to be met in connection with satellite radio communications by a dual band polarization filter can, however, be reduced for a dual band polarization filter used in directional radio. Therefore, a less complicated dual band polarization filter than the one disclosed in U.S. Pat. No. 3,978,434 would suffice for use in directional radio.